﻿Magnetization 
  on 
  the 
  Resistance 
  of 
  Graphite. 
  163 
  

  

  referred 
  to 
  as 
  G 
  I.) 
  as 
  that 
  used 
  by 
  Owen 
  in 
  his 
  researches 
  

   on 
  its 
  thermo-magnetical 
  properties 
  ; 
  a 
  chemical 
  analysis 
  

   gave 
  019 
  per 
  cent, 
  of 
  iron 
  for 
  one 
  of 
  his 
  samples. 
  In 
  

   addition, 
  tests 
  were 
  also 
  made 
  on 
  the 
  following 
  different 
  

   kinds 
  : 
  — 
  

  

  II. 
  Ceylon 
  graphite 
  from 
  the 
  Comptoir 
  mineralogique, 
  

   Geneva, 
  for 
  which 
  I 
  have 
  to 
  thank 
  Prof, 
  du 
  Bois. 
  It 
  was 
  

   easily 
  cleavable 
  but 
  not 
  of 
  a 
  uniform 
  structure, 
  so 
  that 
  the 
  

   cleavage 
  plane 
  was 
  not 
  sufficiently 
  definite. 
  

  

  III. 
  Ceylon 
  graphite 
  from 
  Himbuluwa 
  having 
  internally 
  

   a 
  fine 
  granular 
  structure 
  ; 
  its 
  surfaces 
  were 
  highly 
  polished 
  

   but 
  left 
  no 
  mark 
  when 
  rubbed 
  on 
  paper. 
  For 
  this 
  specimen 
  

   I 
  am 
  indebted 
  to 
  Prof. 
  Grunling*, 
  Munich. 
  

  

  IV. 
  Graphite 
  from 
  the 
  Limberg 
  mine, 
  Pargas 
  (Finland), 
  

   consisting 
  of 
  crystallized 
  flakes 
  imbedded 
  in 
  limestone 
  and 
  

   easily 
  cleavable 
  parallel 
  to 
  their 
  surface. 
  Mr. 
  Magnus 
  

   Wegeliua 
  kindly 
  sent 
  me 
  specimens 
  of 
  this 
  kind. 
  

  

  V. 
  Ceylon 
  graphite, 
  for 
  which 
  I 
  am 
  indebted 
  to 
  Prof. 
  

   Koenigsberger, 
  Freiburg 
  i. 
  B., 
  irregularly 
  cleavable 
  in 
  all 
  

   directions. 
  

  

  VI. 
  Graphite, 
  which 
  had 
  been 
  used 
  by 
  Dr. 
  Reichenheim, 
  

   and 
  which 
  was 
  also 
  sent 
  to 
  me 
  by 
  Prof. 
  Koenigsberger. 
  It 
  

   was 
  not 
  regularly 
  cleavable 
  although 
  small 
  plates, 
  apparently 
  

   crystalline, 
  could 
  be 
  obtained. 
  

  

  Chemical 
  tests 
  for 
  the 
  presence 
  of 
  ferruginous 
  and 
  other 
  

   impurities 
  could 
  not, 
  up 
  to 
  the 
  present, 
  be 
  carried 
  out. 
  

  

  In 
  the 
  investigations 
  on 
  graphite 
  I. 
  short 
  rectangular 
  

   pieces 
  (7-10 
  mm. 
  long, 
  1-2 
  mm. 
  broad, 
  and 
  01-0*5 
  mm. 
  

   thick) 
  were 
  obtained 
  by 
  careful 
  cleavage, 
  and 
  those 
  selected 
  

   for 
  investigation 
  which 
  appeared 
  of 
  most 
  pronounced 
  and 
  

   uniform 
  crystalline 
  structure. 
  

  

  It 
  wjis 
  found 
  only 
  possible 
  to 
  prepare 
  specimens 
  cut 
  

   parallel 
  to 
  the 
  crystalline 
  bases 
  or 
  cleavage 
  plane 
  ; 
  suitable 
  

   pieces 
  with 
  their 
  lengths 
  parallel 
  to 
  the 
  crystalline 
  axis 
  could 
  

   not 
  be 
  obtained. 
  

  

  For 
  the 
  determination 
  of 
  the 
  effect 
  of 
  transverse 
  magnet- 
  

   ization 
  they 
  were, 
  in 
  general, 
  supported 
  in 
  the 
  field 
  so 
  that 
  

   the 
  cleavage 
  planes 
  were 
  perpendicular 
  to 
  the 
  lines 
  of 
  force, 
  

   which 
  were 
  thus 
  parallel 
  to 
  the 
  crystalline 
  axis. 
  On 
  

   supporting 
  the 
  pieces 
  freely 
  in 
  a 
  magnetic 
  field, 
  it 
  was 
  

   observed 
  that 
  they 
  moved 
  bo 
  that 
  the 
  crystallic 
  axi> 
  set 
  itself 
  

   perpendicular 
  to 
  the 
  fiVld, 
  this 
  axis 
  thus 
  coinciding 
  with 
  the 
  

   direction 
  of 
  maximum 
  diamagnetic 
  susceptibility, 
  which 
  

   according 
  to 
  Owen 
  may 
  reach 
  a 
  value 
  of 
  —15 
  millionths. 
  

  

  * 
  A. 
  Grunling, 
  Zeitschr. 
  f. 
  Krist. 
  u. 
  Mineral, 
  xxxiii. 
  p. 
  208 
  (1900). 
  

  

  M 
  2 
  

  

  